The diamine putrescine and the polyamines spermidine and spermine are ubiquitous in animal tissues. They appear to be important compounds in growth and differentiation. Although blood polyamines have been shown to be abnormal in some cancer patients as well as in individuals with cystic fibrosis and to fluctuate in the blood of women as a function of the menstrual cycle, the origin, fate, regulation, and metabolic role have not been defined. Circulating polyamine concentrations are increased in pregnant and lactating rats when compared to virgin animals. Using this animal system studies are being carried out to gain a better understanding of the physiology and biochemistry of circulating polyamines. BIBLIOGRAPHIC REFERENCES: Lundgren, D.W., Hankins, J.M., Ulane, M.M., and Willison, J.W.: Putrescine uptake in cystic fibrosis fibroblasts J. Pediatr. 90:1033-1034, 1977. Cohen, L.F., Lundgren, D.W., and Farrell, P.M., Distribution of spermidine and spermine in blood from cystic fibrosis patients and control subjects. Blood 48:469-475, 1976.